1. Field of the Invention
This invention relates to a flash photographing system and more particularly to a flash photographing system of the type arranged to determine a diaphragm aperture value corresponding to a distance to an object to be photographed by pre-flashing a light before a main flashing action is performed at the determined aperture value.
2. Description of the Prior Art
There have been known photographic flash devices of the type in which a pre-flashing action is performed to detect a distance to an object and to determine a diaphragm aperture value according to the detected distance before a flash photographing operation is carried out at the determined aperture value. In the flash devices of this type, the aperture value is determined according to the distance to the object and a flash photographing operation is carried out at the aperture value so that the flash photography can be always adequately carried out. However, in carrying out photographing with a flash device of this type, if the object is located farther than the distance that can be covered by the light emitting capacity of the flash device, it is hardly possible to effect an adequate exposure even if the aperture value is predetermined by the above stated pre-flashing action.
When the aperture value determined by pre-flashing is smaller than the full-open F-number of the lens in use, the diaphragm cannot be set at the aperture value determined by pre-flashing (a designated aperture value). Then, it is impossible to have a proper exposure also in such a case.
Further, in the case where the object to be photographed is located at a very short distance from the camera, a flash photographing operation results in an over exposure even if it is carried out at an aperture value determined in accordance with the distance determined by pre-flashing.
The flash device of the above stated type has been thus incapable of ensuring a proper exposure in cases where the object to be photographed is located beyond a range of distances detectable by pre-flashing and where the object is located at a very short distance. It is, therefore, desirable for the flash device of this type to be arranged to ensure a proper exposure even for an object located at a long distance. This can be made possible by arranging the flash device to perform the pre-flashing action for determining an aperture value after the main capacitor thereof has been amply charged to impart a sufficient flashing power to the flash device. This arrangement, however, necessitates to inhibit flash photography until the main capacitor has been sufficiently charged. Then, with the flash device arranged in this manner, the photographer tends to miss a shutter chance. Meanwhile, in the case of an object located at a relatively short distance, the main capacitor does not have to be amply charged for obtaining a proper exposure. In spite of this, the arrangement to inhibit the flash photography until the main capacitor is sufficiently charged for an object located at a longer distance deprives the photographer of a shutter chance for photographing an object located at a shorter distance.